This invention relates to the separation of undesired components from a fluid by contacting the fluid with a medium which effects interphase mass and/or heat transfer and the separation of solid or immiscible phase components from the fluid. This invention has particular relationship to such removal by mass and/or heat transfer taking place between counter-flowing fluids through packing or by transmission of the fluids directly through packing.
Mass-transfer or heat transfer operations such as gas scrubbing, distillation, liquid-liquid extraction and the like are carried out by counterflow of fluid phases such as a gas and a liquid between which the mass transfer is to take place through a medium whose purpose is to maximize the contact surface or area between the gas and liquid without blocking the gas flow altogether by so-called flooding. Flooding is defined as the limiting condition which occurs when, as gas or liquid flows are increased, the gas phase becomes discontinuous, the gas-pressure drop becomes unstable, and the bed tends to fill with liquid. A similar phenomenon occurs in liquid-liquid extraction operations in which the dispersed lighter phase can no longer ascend and coalesces to block continuous-phase flow. Common types of prior-art packing materials include such bodies as Raschig rings and Berl and Intalox saddles as disclosed in Leva U.S. Pat. No. 2,639,909. These common packings are effective as liquid dispersal surfaces, but have the disadvantage of relatively high gas flow resistance and a susceptibility to flooding at relatively low rates of gas and liquid flow. Design fluid-flow capacities of packed towers are based principally on two criteria: the flood limit and the intrinsic gas-flow resistance of the packing. (B. J. Lerner and C. S. Grove, Jr., Industrial and Engineering Chemistry, Vol. 43, pages 216-225, Jan. 1951.) A consequent disadvantage of such conventional packings in the smaller sizes is the need for uneconomically large tower-shell diameter required to keep the gas velocity below the flooding point or to keep gas-flow resistance and dependent blower costs within economic limits.
In recent years, commercial packed-tower design practice has been directed toward obtaining higher gas velocities, or low gas flow resistance, and thus more economic smaller tower-shell diameters. Typical of the teachings of the prior-art attempts to meet this objective are:
Kleinschmidt U.S. Pat. No. 2,143,016 PA1 Smucker U.S. Pat. No. 2,607,714 PA1 Dixon U.S. Pat. No. 2,615,832 PA1 Teller U.S. Pat. No. 2,867,425 PA1 Keeping U.S. Pat. No. 2,921,776 PA1 Robjohns U.S. Pat. No. 3,293,174 PA1 Lerner U.S. Pat. No. 3,410,057 PA1 Lipinski U.S. Pat. No. 3,438,614
These patents disclose beds of randomly disposed packing materials for extending the surface contact between the phases taking part in the mass transfer. Lower gas-flow resistances and higher gas-flow velocities have been achieved through the use of larger sizes of conventional tower packings such as saddles, and the use of more "open" distributed-surface packings such as Pall rings and Tellerettes (Teller), which flood at much higher liquid and gas flow rates than do the older types of packings. However, in the use of mass and heat transfer columns including packing of this prior-art type there has been experienced the emission of liquid spray in large quantities from the top of the columns which militates against transfer efficiency.
It is an object of this invention to provide high-capacity, high-efficiency mass-transfer packed columns or beds or towers which shall transmit the gas at relatively high velocities, without excessive gas flow resistance, shall not flood until the liquid and gas-flow rates reach relatively high magnitudes, and shall not emit spray in large quantities from the top of the columns. It is also an object of this invention to provide a packed bed or column for effectively separating suspended solids or an immiscible dispersed phase from fluids, for example, turbidity from drinking water, mist droplets from gas or oil droplets from an aqueous liquid which has been exposed to oil.